As for countries including our country that have entered or are entering super-aged society, it has been critically important to develop medical devices for maintaining and controlling healthy life expectancy. In recent years, wearable electronics for the purpose of continuously measuring biological information have been developed in an accelerated manner. And, wearable devices such as wristwatch-type heart rate meters and blood sugar level sensors have been put to practical use (e.g. Non-patent Literature 1).
There is also being developed a technique where a flexible substrate is used to directly fix an electronic device to an arm, a leg and other parts. For example, as an electronic device capable of undergoing curvature deformation, there has been proposed a flexible substrate that is formed using a resin film having a comb-like portion composed of a plurality of protrusions (e.g. Patent Literature 1). Further, there has also been proposed an LED device (e.g. Patent Literature 2) manufactured in the following manner. That is, a light-emitting diode is to be embedded in an encapsulation resin layer, followed by placing a barrier film layer thereon so as to form an encapsulation sheet, and then thermally compressing such encapsulation sheet onto a substrate through flat press.
As a more advanced configuration, studies have also been made on a type of device capable of acting like a sticker, and thus being attached to a highly stretchable biological tissue such as skin. It has been pointed out that by employing a thin film exhibiting the same level of stretching rate as epidermis, the device can be fixed to the skin without causing any uncomfortable feeling (e.g. Non-patent Literature 2).
Further, as examples of devices using thin films, there have been reported case examples where circuit boards were manufactured using thin films having a thickness of several μms, such as those made of polyvinyl alcohol, polyethylene naphthalate and parylene-C (e.g. Non-patent Literatures 3 to 5).